Republican mega-donor David Koch, who helped pioneer a network of often surreptitious organizations aimed at influencing elections and public policy, leaves behind a legacy of dark-money groups and a volatile political landscape.

Koch, one half of the Koch Brothers along with his older brother Charles, died at age 79, the billionaires’ company, Kansas-based Koch Industries, said Friday. David Koch had stepped away from business and politics in 2018 for health reasons and had previously battled cancer, though the company did not say the exact cause of death.

Congressional and K Street insiders, whether they agreed with the Kochs’ libertarian-conservative ideology or fought it relentlessly, agreed that David Koch left a lasting imprint on the nation’s politics.

The flush-with-money Koch network, which includes such groups as Americans for Prosperity, helped to resuscitate the Republican Party after its losses in the 2008 presidential and congressional elections and helped give rise to the tea party movement. But David Koch died at a time when the emboldened Republicans’ current leader, President Donald Trump, doesn’t toe the Koch line, especially when it comes to trade and immigration policy.

In establishing AFP and the Koch network, “you could fairly say he saved the Republican Party after that incredible defeat,” said David McIntosh, president of the conservative Club for Growth, referring to the 2008 elections. “He helped the Republican Party get back on its feet.”

David Koch’s biggest, most lasting influence is likely to be the system of using nonprofit organizations that often do not need to disclose their donors. The Koch network made use of Supreme Court rulings, such as the landmark 2010 Citizens United case, that allowed corporations to spend unlimited money. But they also worked through organizations that could shield donors from public view.

Though they pioneered the effort, they have been widely copied on both sides of the aisle.

“By far, the most fundamental way that David Koch and his brother and their network has influenced campaign finance broadly is through the role that they played in expanding the way that dark money enters elections,” said Sarah Bryner, who has tracked Koch political spending as research director at the nonpartisan Center for Responsive Politics. “That’s what I think of when I think of Koch money — those networks and the chains of connections and the ways in which they are able to spend millions and millions of dollars out of the public view.”

Still, some of the money is traceable to some extent to the Kochs’ network of groups, which include nonprofit social welfare organizations, super PACs and other outside entities with various rules for public disclosures.

Americans for Prosperity reported spending some $13.3 million and Freedom Partners reported $30 million to the Federal Election Commission for political advertising in 2016, the center has found. The Kochs said they would spend $400 million in the 2018 elections, but just $44.2 million was disclosed to the FEC, the center’s research showed.

Club for Growth’s McIntosh recalled that he first met David Koch in the 1990s when McIntosh was a GOP congressman from Indiana. Koch, he said, invited him and his wife, Ruthie, to New York.

“He was very encouraging,” McIntosh said. “He was always looking for young people to get involved and take leadership roles. That’s a huge part of the legacy of the Koch Network: to bring droves of young people into the conservative and libertarian movement and Republican politics.”

David Koch ran for vice president, on the Libertarian Party ticket, in 1980, but found the Republican Party the closest and most viable political home, McIntosh and others said.

In addition to funding political causes and candidates, David Koch, who lived in New York, donated millions to artistic and medical caucuses with his name on several spots including the David H. Koch Theater at the Lincoln Center for the Performing Arts. But it’s his role in politics that won him the most fame.

“The Kochs, and you’ve got to talk about Charles and David together, they revolutionized much of money in politics,” said Burdett Loomis, an emeritus professor of politics at the University of Kansas. “They certainly moved politics, with their money, to the right.”

Though the Kochs may be at odds with Trump Republicans on issues of trade and immigration, they were big backers of a criminal justice overhaul that won Trump’s blessing and was enacted in December.

Despite policy divisions with the Trump administration, the Kochs backed some of the administration’s insiders, including Secretary of State Mike Pompeo, a former Kansas congressman.

“Certainly, the Kochs were instrumental in the rise of the farther right politics in Kansas,” Loomis said, noting the Koch Brothers’ work through state-focused organizations, including the American Legislative Exchange Council.

The Kochs’ donor retreats also helped expand their own influence, urging other business leaders to give in lockstep.

David Koch and his brother Charles “have been staunch proponents for spending as much money in politics in every avenue you can,” said Lisa Gilbert, a frequent opponent of the Koch network as vice president of legislative affairs at the liberal group Public Citizen. “They sort of led the charge in explaining how to do that to other corporate interests.

“In terms of laying a path that corporate America has followed, that does not go away with the death of the single person,” she added.

McIntosh agreed that David Koch’s imprint will endure.

“He made sure there was a political force for freedom and liberty that survived past his lifetime,” McIntosh said. “In a personal way, he was such a warm and gracious man.”